I am working on the dial drive for this rig. The LMO is a TRW 800 651.

In setting the dial pointer to track across the 0-5 dial window, I have
found that the LMO only makes (4) 360 deg rotations, not 5, as called
out in the instructions. There are a series of 6 little "L" shaped
pawls on the LMO shaft. On rotation (1), the inner-most pawl is stopped
by a roll pin on the shaft bracket, but on rotation (2) it appears that
(3) of the pawls are stopped by the first pawl. There after, one pawl
is stopped by the preceeding pawl on each rotation.

None of the pawls seems to be distorted or bent in such a way as to
interfer with the rest passing over it as they should.

This description will probably make sense to an expert- I suppose not
to anyone else!

Anybody incounter this before??

On 12 Sep 2006 20:52:13 -0700, sargent wrote in .com:
I am working on the dial drive for this rig. The LMO is a TRW 800 651.

In setting the dial pointer to track across the 0-5 dial window, I have
found that the LMO only makes (4) 360 deg rotations, not 5, as called
out in the instructions. There are a series of 6 little "L" shaped
pawls on the LMO shaft. On rotation (1), the inner-most pawl is stopped
by a roll pin on the shaft bracket, but on rotation (2) it appears that
(3) of the pawls are stopped by the first pawl. There after, one pawl
is stopped by the preceeding pawl on each rotation.

None of the pawls seems to be distorted or bent in such a way as to
interfer with the rest passing over it as they should.

This description will probably make sense to an expert- I suppose not
to anyone else!

Anybody incounter this before??

This sounds much like the hardware that limits rotation on an R-390 or
R-390A Kilocycles knob to 10 (or is it 11?) turns, and which also is
subject to similar troubles.

With the LMO at one end of travel, so that all the pawls are free to
move, can you move them by hand to see what is causing them to hang
up when they shouldn't? If they're just gummed together by thickened
lubricant, it might be a fairly simple job (Ha!) to put a few frops
of carefully-chosen solvent on them and free them up.

--
Mike Andrews, W5EGO

Tired old sysadmin

This description will probably make sense to an expert- I suppose not
to anyone else!

Anybody incounter this before??

Yes, that mechanism is called a Geneva wheel. and it's most likely that
either the first or last "washer", is locking up and not rotating due to
grease congealing and either locking it to the front or back plate or to
another wheel and 2 rotating at a time.

I have a couple of those LMO's if all else fails, but expect that as the
other poster suggests, a drop of WD-40 would cure your problem.

Regards
W4ZCB

Harold E. Johnson wrote:
This description will probably make sense to an expert- I suppose not
to anyone else!

Anybody incounter this before??

Yes, that mechanism is called a Geneva wheel.

Well, actually, no it isn't a Geneva wheel, but it performs the same purpose.
A Geneva wheel, actually called a Geneva Stop Work, is a Maltese cross shaped
wheel that is used in conjunction with a rotating pawl. As the pawl rotates,
it flips the Maltese cross shaped wheel one tooth per revolution. The final
tooth on the Maltese cross is oversized, and will block the shaft from turning
when it is reached. The cross can have more than 4 petals.

and it's most likely that
either the first or last "washer", is locking up and not rotating due to
grease congealing and either locking it to the front or back plate or to
another wheel and 2 rotating at a time.

I have a couple of those LMO's if all else fails, but expect that as the
other poster suggests, a drop of WD-40 would cure your problem.

I would bet you are right about that!

-Chuck

Chuck Harris wrote:

I have a couple of those LMO's if all else fails, but expect that as the
other poster suggests, a drop of WD-40 would cure your problem.

I would bet you are right about that!

WD-40 will loosen up the old grease, but after a while it will evaporate
and just congeal again. I recommend first using WD-40 or something similar
to get the old gunk out, and maybe a naptha soak if you want to pull it
apart. Get all of that out, then try something like Permatex Superlube
spray to get some new lubricant in there.

WD-40 is a great solvent and water dispersal agent, but it's a lousy
lubricant and it eventually evaporates and leaves gummy varnish behind.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."